Download Lab 2-3: Interpreting a Controlled Experiment

Fishy Frequencies
Purpose: To use fish crackers to help build your understanding of
natural selection and the role of genetics & gene frequencies in evolution.
Standards:
a. Students know why natural selection acts on the phenotype rather than the genotype of an
organism. a. Students know how natural selection determines the differential survival of groups of organisms. b.
Students know a great diversity of species increases the chance that at least some organisms survive major changes
in the environment. d. Students know reproductive or geographic isolation affects speciation.
Background: These little fish are natural prey of the terrible fish-eating sharks
(that’s you). Fish come in two phenotypes gold and ____________. The Gold fish
are have a gene that makes then swim faster. New fish are born every “year,” the
birth rate equals the death rate. You will simulate births by reaching into the
“ocean” of spare fish and choosing the replacement fish randomly.
Materials: Two types of fish crackers and container to represent ocean. Data table
plus a paper towel to represent the pond.
Procedure:
Part I – No Selection
1. Randomly choose a study population of 10 fish from the “ocean.”
2. Count the gold and brown fish in your initial population of ten and
record your individual data. Do not go on to the next step until the
class data has been pooled and recorded.
3. Eat three fish; be sure to choose randomly.
4. Add three fish from the “ocean;” be sure to choose randomly!
5. Count gold fish and brown fish in the restored population and record
your data and class data.
6. Again, eat three fish choosing randomly.
7. Add three randomly selected fish, one for each death.
8. Count and record data. Record class data.
9. Repeat steps 6,7, & 8 three more times.
10. Fill in the data
Part II – Selection
1. Randomly choose a population of ten fish from the “ocean.”
2. Count the gold and brown fish in your initial population of ten and
record your individual data. Do not go on to the next step until the
class data has been pooled and recorded.
3. To simulate selection, the predator will no longer eat randomly. You,
the terrible fish-eating sharks, much prefer to eat gold fish; you eat
ONLY gold fish unless none are available, forcing you to eat brown fish
in order to stay alive. Eat three gold fish; if you do not have three, eat
brown fish for a total of three!
4. Add three fish form the “ocean”; be sure to choose replacements
randomly!
5. Count gold and brown fish in the restored population and record your
data and class data.
6. Again, eat three gold fish; if you do not have three, eat brown fish for a
total of three.
7. Add three randomly selected fish, one for each death.
8. Count and record data. Record class data.
9. Repeat steps 6, 7 & 8 three more times.
10. Fill in the data table with calculated frequencies (take the number of
that color and divide by the total)
Data:
No Selection
Generation
# ______
fish
# gold
fish
Total Fish
Frequency
of ________
Frequency
of Gold
# gold fish Total Fish Frequency
of ________
Frequency
of Gold
Initial 1
2
3
4
5
6
Selection
Generation
# ______
fish
Initial 1
2
3
4
5
6
Analysis:
1. Make a graph that shows the frequency of color of fish over each
generation.
2. What is evolution?
3. What is natural selection?
4. Compare the frequencies of fish when there is no selection.
5. Compare the frequencies of fish when there IS selection.
6. Which fish had a greater chance of survival and why? In other words
what gene is favored?
7. Explain what is meant by “differential survival and reproduction” and
how this lab demonstrates this them..
8. Explain what would happen if selective pressure changed and the
recessive trait offered a selective advantage (was selected for)?
9. Evaluate this simulation by listing the ways in which it faithfully reflects
changes in gene frequencies that might occur in nature AND identifying it
shortcomings.
Name : ___________________________ Date: ___________ Per. _____
Background: These little fish are natural prey of the terrible fish-eating
sharks (that’s you). Fish come in two phenotypes gold and __________. The
Gold color is a recessive trait and is genotype ff. These fish are yummy and
easy to catch. The __________ trait is dominant and can be genotype FF or Ff.
These fish are salty, sneaky and hard to catch. New fish are born every “year,” the birth
rate equals the death rate. You will simulate births by reaching into the “ocean” of spare
fish and choosing the replacement fish randomly.
Data:
No Selection
Generation
# ______
fish
# gold
fish
Total Fish
Frequency
of ________
Frequency
of Gold
# gold fish Total Fish Frequency
of ________
Frequency
of Gold
Initial 1
2
3
4
5
6
Selection
Generation
# ______
fish
Initial 1
2
3
4
5
6
Analysis:
1. Make a graph that shows the frequency of color of fish over each
generation.
2. What is evolution?
3. What is natural selection?
4. Compare the frequencies of fish when there is no selection.
5. Compare the frequencies of fish when there IS selection.
6. Which fish had a greater chance of survival and why? In other words
what gene is favored?
7. Explain what is meant by “differential survival and reproduction” and
how this lab demonstrates this them.
8. Explain what would happen if selective pressure changed and the
recessive trait offered a selective advantage (was selected for)?
9. Evaluate this simulation by listing the ways in which it faithfully reflects
changes in gene frequencies that might occur in nature AND identifying it
shortcomings.